How to distinguish Sapphire crystal watch glass?

As we all know the sapphire crystal on watch is not natural sapphire from mine. it is synthetic crystallized aluminum oxide. but it has the same features as natural one.

Watch Glass material also have several options. before 60's, all watches were in acrylic or plastic glass. which is flexible to any shape and easy to be scratched but also okey to buff it by tool. it has long history to be watch glass. then Hardened Mineral Watch Glass came out with heat, it is much stronger and anti-scratch than plastic one.

then in new century, a new material as watch glass to be popular suddenly. after these high luxury brands change to new Sapphire Watch Glass gradually. it became a new fashion. It is anti-scratch feature to make it as a perfect glass for high end watches. esp new microbrands put it as good sell point even it is quartz watch. as flat sapphire watch glass is not so expensive than Single-domed or Double domed Watch Glass. it is not something can't bear at all for medium class watches. for us, we prefer to use the sapphire crystal as watch len for Mechanical Wrist Watches instead of mineral watch glass.

then there is a new problem. how to distinguish the sapphire watch glass?

There are 3 ways to test it. first 2 ways can be done by anyone. no need the tool.

1. put a drop of water on glass, if it stays or slips off slowly. it means it is sapphire crystal. if spread quickly, it means not sapphire len.

2. put the watch glass touch your face which it is very sensitive. if it is cold feeling, it is sapphire crystal.

3. use the diamond selector, it is a tool to check the hardness of diamond for Mohs scale. Mineral Glass is 5, Sapphire was 9, Diamond is 10. Sapphire is most hardest material in the earth. due to hardness, this is why so high scratch resistance. only Diamond can scratch surface of sapphire crystal.

Let's do it and check the watch glass on your watch.